1. Field of the Invention
The present invention relates to a gate driver circuit for MOS gated devices, and more specifically to a monolithic gate driver circuit for MOS gated devices, particularly those used in fluorescent lamp ballast circuits.
2. Description of the Related Art
Electronic ballasts for gas discharge circuits have recently come into widespread use because of the availability of power MOSFET switching devices and insulated gate bipolar transistors ("IGBTs") to replace previously used power bipolar switching devices. Monolithic gate driver circuits, such as the IR2155 sold by International Rectifier Corporation and described in U.S. Pat. No. 5,545,955, the disclosure of which is incorporated herein by reference in its entirety, have been devised for driving the power MOSFETs or IGBTs in electronic ballasts. The IR2155 gate driver IC offers significant advantages over prior circuits in that it is packaged in a conventional DIP or SOIC package and contains internal level shifting circuitry, under voltage lockout circuitry, deadtime delay circuitry, and additional logic circuitry and inputs so that the driver can self-oscillate at a frequency determined by external resistors R.sub.T and capacitors C.sub.T.
Although the IR2155 offers a vast improvement over prior ballast control circuits, it lacks a number of desirable features such as: (i) a start-up procedure which ensures a flash-free start without an initial high voltage pulse across the lamp, (ii) non-zero voltage switching protection circuitry, (iii) over temperature shutdown circuitry, (iv) DC bus and AC on/off control circuitry, and (v) near or below resonance detection circuitry.